Donors have the option to cover the transaction (WePay) fees for their donations. Clicking the 'Cover transaction fees' button will automatically calculate and tell the donor how much their payment will increase in order to cover the fee.

When donors opt to cover the transaction fee, the fee is applied to the total of their payment, which is their donation + the standard transaction fee.

So for a $100 donation, the standard transaction fee is $3.10. This means that the total amount that the fee is applied to is $103.10, not $100 - The donor pays the fee on the fee as well. This is to get the organization as much of the donation as possible.